Micro-electro mechanical light modulator device

ABSTRACT

A micro-electro mechanical light modulator device includes a movable reflective plate, a fixed partial reflective plate, an optical gap defined between the reflective plate and the fixed plate, and an actuator configured to move the reflective plate through an operating range wherein a neutral state position of the reflective plate approximately corresponds to a black state value of the optical gap.

BACKGROUND

Micro-electromechanical systems (MEMS) are used in a variety ofapplications such as optical display systems. Such MEMS devices havebeen developed using a variety of approaches. In one approach, adeformable deflective membrane is positioned over an electrode and iselectrostatically attracted to the electrode. The gap between the twoelectrodes determines the output of the device. Accordingly, the outputof the device is controlled by controlling the gap distance.

One approach for controlling the gap distance between electrodes is toapply a continuous control voltage to the electrodes, wherein thecontrol voltage is increased to decrease the gap distance, andvice-versa. In such approaches the gap distance changes as chargeaccumulates on the electrodes, creating an electrostatic forcetherebetweeen. This electrostatic force is opposed by a mechanicalrestoring force provided by the deflection of flexures that supports oneof the electrodes. This approach suffers from electrostatic instabilitythat greatly reduces a usable operating range over which the gapdistance can be effectively controlled. This is because the electrodesform a variable capacitor in which capacitance increases as the gapdistance decreases.

When the gap distance is reduced to a certain threshold value, usuallyabout two-thirds of an initial gap distance, the electrostatic force ofattraction between the electrodes overcomes the mechanical restoringforce causing the electrodes to “snap” together or to mechanical stops.This is because at a distance less than the minimum threshold value, thecapacitance is increased to a point where excess charges are drawn onthe electrodes resulting in increased electrostatic attraction. Thisphenomenon is known as “charge runaway.”

As introduced, the electrodes are sometimes snapped to mechanical stops.The size of the optical gap when the electrodes are in contact with themechanical stops often corresponds to the black state size of theoptical gap, such that when the electrodes are in this position, thedevice absorbs light incident thereon. This mechanical contact mayresult in the electrodes sticking together (or stiction). Further, thiselectrical contact may also result in spot welding. Accordingly, thecontact may reduce the reliability and/or operating life of a device andconsequently the display system that makes use of such a device.

SUMMARY

A micro-electro mechanical light modulator device includes a movablereflective plate, a fixed partial reflective plate, an optical gapdefined between the reflective plate and the fixed plate, and anactuator configured to move the reflective plate through an operatingrange wherein a neutral state position of the reflective plateapproximately corresponds to a black state value of the optical gap.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of the presentapparatus and method and are a part of the specification. Theillustrated embodiments are merely examples of the present apparatus andmethod and do not limit the scope of the disclosure.

FIG. 1 illustrates an exemplary display system.

FIG. 2A illustrates an exemplary light modulator device in a neutralposition state position.

FIG. 2B illustrates the light modulator device of FIG. 2A in which thereflective plate is at an intermediate position within the operationaldisplacement range of the reflective plate.

FIG. 2C illustrates the light modulator device of FIGS. 2A-2B in whichthe reflective plate is at an extreme position of the operationaldisplacement range of the reflective plate.

FIG. 3 illustrates a top view of the light modulator device of FIGS.2A-2C showing the pinwheel support structure in more detail.

FIG. 4 is a flowchart illustrating an exemplary method of forming alight modulator device.

FIG. 5 illustrates an exemplary light modulator device that includespiezo-electrically actuated flexures.

FIG. 6 illustrates an exemplary light modulator device that includes amagnetically controlled reflective plate.

FIG. 7 illustrates a schematic view of a display system according to oneexemplary embodiment.

FIG. 8 illustrates a light modulator device according to one exemplaryembodiment.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

Several exemplary light modulator devices are described herein that mayimprove the reliability of a display system by providing non-contactoperation. Non-contact operation refers to minimizing or eliminatingcontact between individual parts or components of the light modulatordevice, such as a reflective plate. Non-contact operation minimizesstiction or spot welding associated with contact between individualcomponents or parts of the light modulator device. According to severalexemplary embodiments, an optical gap and an electrical gap areseparated to provide non-contact operation.

The sizes of the optical gap and electrical gap are varied by adjustingthe position of a reflective plate. Several different support structuresmay be used to support the reflective plate as it moves through itsoperational displacement range. Further, according to several exemplaryembodiments, the neutral position of the reflective plate approximatelycorresponds to the black state position of the light modulator device.In some of such embodiments, the position of the reflective plate iscontrolled by electrostatic forces. Other embodiments make use ofpiezo-electric actuators or magnetically controlled actuators to controlthe position of the reflective plate.

The operational displacement range refers to the distance the reflectiveplate travels between a black state position and the position of thereflective plate corresponding to the maximum optical gap.

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present method and apparatus. It will be apparent,however, to one skilled in the art, that the present method andapparatus may be practiced without these specific details. Reference inthe specification to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment is included in at least one embodiment. Theappearance of the phrase “in one embodiment” in various places in thespecification are not necessarily all referring to the same embodiment.

Display Systems

FIG. 1 illustrates an exemplary display system (100). The components ofFIG. 1 are exemplary only and may be modified or changed as best servesa particular application. As shown in FIG. 1, image data is input intoan image processing unit (110). The image data defines an image that isto be displayed by the display system (100). While one image isillustrated and described as being processed by the image processingunit (110), it will be understood by one skilled in the art that aplurality or series of images may be processed by the image processingunit (110). The image processing unit (110) performs various functionsincluding controlling the illumination of a light source (120) andcontrolling a spatial light modulator (SLM) (130). The SLM (130) willnow be discussed in more detail.

The SLM (130) includes an array of micro-electro mechanical (MEM)devices, or light modulator devices, which have optical cavities definedtherein. Each optical cavity has an optical gap formed between twoopposing reflectors. The size of the gap is controlled by balancing aspring force and an electrostatic force between the two reflectors.Light that enters each light modulator device is modulated ormanipulated to achieve desired characteristics. These characteristics,which include the hues and intensities of the transmitted light, aremanipulated by varying the gap between the reflectors.

Returning to the operation of the display system (100) in general, theSLM (130) manipulates incoming light to form an image-bearing beam oflight that is eventually displayed or cast by display optics (140) on aviewing surface (not shown). The display optics (140) may comprise anydevice configured to display or project an image. For example, thedisplay optics (140) may be, but are not limited to, a lens configuredto project and focus an image onto a viewing surface. The viewingsurface may be, but is not limited to, a screen, television, wall,liquid crystal display (LCD), or computer monitor. The light modulatordevice structures described herein allow the size of the reflectors tobe precisely controlled while minimizing or eliminating undesiredcontact between the two reflectors and/or other parts of the lightmodulator device. This control also includes the control of the blackstate of the light modulator device.

Non-Contact Mode Micro-Electro Mechanical

FIGS. 2A-2C illustrates the operation of a single light modulator deviceor light modulator device (200). The light modulator device (200)includes a reflective plate (205) and a fixed electrode plate (210)separated by a non-optical gap, such as an electrical gap (215). Thelight modulator device (200) also includes a top plate (220) that isseparated from the reflective plate (205) by an optical gap (225).Decreasing the size of the electrical gap (215) increases the size ofthe optical gap (225). As will be discussed in more detail below, thelight modulator device (200) is configured to allow the reflective plate(205) to move between a black state position and a maximum colordisplacement value while minimizing or eliminating contact between thereflective plate (205) and other parts of the light modulator device(200). The configuration of the light modulator device (200) will now bediscussed in more detail.

The light modulator device (200) is supported by a substrate (230). Forexample, a support structure supports the reflective plate (205) and anoutside support structure supports the top plate (220). In particular,the fixed electrode plate (210) is supported by the substrate (230).Posts (235) are also supported by the substrate (230). Flexures (245)are coupled to the posts (235) and support the reflective plate (205)above the substrate. Supports (250) are coupled to the posts (235) suchthat the supports (250) suspend the top plate (220) above the reflectiveplate (205). The flexures (245) may be any suitable flexible material,such as a polymer, a metal or single crystal silicon, that has linear ornon-linear spring functionality. For example, the flexures (245) may bepart of a pin-wheel type support structure, as will be discussed in moredetail with reference to FIG. 3.

The light modulator device shown (200) functions as a Fabry-Perot lightmodulator. As a result, a portion of the top of reflective plate (205)is treated with a highly reflective coating (255) while a portion of theunderside of the top plate (220) is treated with a partially reflectivecoating (256). A portion of a beam of light incident on the lightmodulator device (200) will pass through the top plate (220) and bepartially reflected by the partially reflective coating (256) on theunderside of the top plate (220) while another portion of the beam oflight will pass through the top plate (220) and the partially reflectivecoating (256) and into the optical gap (225).

Once the light enters the optical gap (225), it is bounced between thepartially reflective coating on the underside of the top plate (220) andthe highly reflective coating on the reflective plate (205). Each timethe light inside the optical gap (225) becomes incident on the partiallyreflective top plate (220), some portion of the light passes through thepartially reflective coating and the top plate (220) and escapes thelight modulator device (200). The wavelengths of the light that are thusable to pass through the top plate (220) depend at least in part on thesize of the optical gap (225). Accordingly, varying the size of theoptical gap (225) controls the characteristics of light that exits thelight modulator device (200).

The size of the optical gap (225) is controlled by movement of thereflective plate (205). The optical gap (225) of the light modulatordevice (200) shown in FIGS. 2A-2C may be precisely controlled over abroad range of displacements, or an operating displacement range, whileminimizing or eliminating contact between the reflective plate (205).This operational displacement range includes movement from a neutralposition to produce a black state response through positions forproducing light of selected wavelengths within the visible spectrum. Therelative position of the reflective plate (205) and correspondingoptical gap and the electrical gap will first be discussed withreference to a black state/neutral state position, followed by adiscussion of intermediate displacement positions and the extremedisplacement positions.

FIG. 2A shows the light modulator device (200) in a neutral stateposition. A neutral state position refers to the relative position ofeach of the light modulator device's components in the absence of aforce applied to the reflective plate (205). The neutral state positionof the light modulator device (200) may correspond to the black stateposition of the reflective plate (205). In particular, as shown in FIG.2A, the flexures (245) are not substantially deflected in response toelectrostatic force between the reflective plate (205) and the fixedelectrode plate (210). In particular, the reflective plate (210) and thetop plate (220) are coupled to the same reference voltage. As a result,the light modulator device (200) is in its neutral state when noelectrostatic force is established between the reflective plate (205)and the top plate (220) and the fixed electrode plate (210) and thereflective plate (205) have little or no electrostatic force betweenthem.

The optical gap (225) in this configuration is at its minimum size. Morespecifically, the optical gap (225), may be between about 50-200 nm, orapproximately 100 nm, which allows the light modulator device (200) toabsorb sufficient light to be in a black state. For example, the size ofthe optical gap (225) while the reflective plate (205) is in a blackstate position allows the light modulator device (200) to trapessentially all of the light that enters therein, such that the lightmodulator device produces black output. Accordingly, the light modulatordevice (200) may be reliably placed in its black state while minimizingor eliminating the need for the use of bumps, posts, or otherprotrusions to maintain the proper gap distance. The black stateposition thus introduced may be considered as a default black state gap.This gap can be adjusted by controlling the size of the optical gap(225).

As previously introduced, controlling the size of the optical gap (225)controls the output of the light modulator device (200). Accordingly, inaddition to establishing the neutral state position of the reflectiveplate (205) to correspond with the black state response of the lightmodulator device (200), the neutral state position may cause the opticalgap (225) at a neutral state position to be smaller than at the blackstate response. In such a case, the black state response may then becontrolled by controlling the electrostatic force between the reflectiveplate (205) and the fixed electrode plate (210). Further, as previouslydiscussed, the size of the optical gap (225) shown in FIGS. 2A-2Cdepends, at least in part, on the size of the electrical gap (215).These relative positions will now be discussed in more detail.

Establishing electrical charge on the plates (205, 210) varies theoptical gap (225), such that a desired wavelength at a desired intensitymay be selected. The flexures (245) allow the electrical gap (215) tovary when charge is stored on the plates (205, 210). The charge storedon the plates (205, 210) results in an electrostatic force between theplates (205, 210), thereby drawing the reflective plate (205) toward thefixed electrode plate (210). This force is opposed by the spring forceassociated with the deflection of the flexures (245). When anelectrostatic force exists between the plates (205, 210), the reflectiveplate (205) will continue to be drawn toward the fixed electrode plate(210) until the spring force and the electrostatic force reachequilibrium. When these two forces reach equilibrium, the reflectiveplate (205) will be held in this position. One possible intermediateposition of the reflective plate (205) is shown in FIG. 2B. Accordingly,the relative position of the reflective plate (205) with respect to thefixed electrode plate (210) and the top plate (220) may be varied by theamount of charge applied to the plates (205, 210). Once theelectrostatic force is released, such as by dissipating the accumulatedcharges, the spring force returns the flexures (245) to a neutral stateposition. While the present exemplary embodiment has been discussed withreference to establishing an electrostatic force between the plates,those of skill in the art will appreciate that an electric field may beestablished between the plates such that the size of the electric gap iscontrolled with bias.

As previously introduced, the reflective plate (205) is moved about arange of positions to control the output of the light modulator device(200) in response to control signals from the image processing unit(110; FIG. 1). FIG. 2C illustrates the reflective plate (205) near oneextreme of its range of motion. As shown in FIG. 2C, at this position,the instantaneous electrical gap (215) is substantially more than ⅔ thesize of the electrical gap when the reflective plate (205) is in theneutral state location shown in FIG. 2A. As a result, the electrical gap(215) at the neutral position is approximately three times as large asthe operational displacement range of the reflective plate (205).Accordingly, the reflective plate (205) moves through a range of motionwhile maintaining an electrical gap (215) that is above the minimumthreshold to prevent the reflective plate (205) from snapping to theelectrode plate (210) when the reflective plate (205) is controlled bybias control.

As a result, the light modulator device (200) is able to provide bothblack state responses and normal operating state responses whileminimizing or eliminating contact between the reflective plate (205) andother parts of the light modulator device (200). In addition, the topsurface of the reflective plate (205) and the bottom surface of topplate (220), which are adjacent the optical gap (225), may be coatedwith dielectric materials. These surfaces may be coated with a layer ofprotective material (255), such as a layer of dielectric material,because the optical gap (225) and the electrical gap (215) areseparated. More specifically, the bottom surface of the reflective plate(205) and the top surface of the fixed electrode plate (210) areadjacent the electrical gap (215). Consequently, these surfaces are thesurfaces that have electrostatic charge accumulated thereon to providethe electrostatic forces discussed above.

The top surface of the conductive plate (205) and the bottom surface oftop plate (220) in the exemplary embodiment shown in FIGS. 2A-2C do notaccumulate charges and therefore may be coated with protective layers(257, 258). The protective layers (257, 258) may be useful in protectingthe top plate (220) and/or the reflective plate (205) during formationand/or use of the light modulator device (200). The protective layers(257, 258) are shown separated from the highly reflective coating (255)and the partially reflective coating (256) to emphasize that multiplelayers may be applied.

According to other exemplary embodiments, the top plate (220) is coupledto a voltage source that may be different than the voltage sourcecoupled to the reflective plate (205). In such an embodiment, theneutral state position of the reflective plate (205) may be adjusted byestablishing a potential between the reflective plate (205) and the topplate (220). Accordingly, the voltage difference between the reflectiveplate (205) and the top plate (220) may be used to fine tune the blackstate response of the light modulator device (200).

Accordingly, the configuration of the present light modulator device(200) allows the light modulator device (200) to modulate light,including black state display, while minimizing or eliminating contactbetween the reflective plate (205) and other parts of the lightmodulator device (200). Minimizing or eliminating contact betweencomponents minimizes stiction or other adverse affects, which maydecrease the reliability and operating life of the light modulatordevice (200). As previously introduced, the flexures (245) allow thereflective plate (205) to move, thereby varying the size of theelectrical gap (215) and the optical gap (225). Several supportstructures may be employed to allow this movement, including a pinwheeltype support structure, which is shown in more detail in FIG. 3.

Pinwheel Flexure Structure

FIG. 3 illustrates a top partial cutaway side view respectively of alight modulator device (200) incorporating a pinwheel flexure structure(300). In particular, the supports (250) and the top plate (220) havebeen cutaway to focus on the pinwheel flexure structure (300). Thereflective plate (205) is suspended over the fixed electrode plate (210;FIGS. 2A-2C) by the posts (235) which extend from the substrate (230;FIGS. 2A-2C) in a pinwheel configuration. In this configuration, theflexures (245) extend from the posts (235) to the corners of thereflective plate (205) to thereby suspend the reflective plate (205).

As an electrostatic force is established between the reflective plate(205) and the fixed electrode plate (210), the flexures (245) deflect inresponse to the force, thereby allowing control of the size of theoptical gap (225) as discussed above. While a pinwheel cantilever ortorsional-type flexure structure (300) has been discussed above, anynumber of support structures may be used. Some other exemplary supportstructures include, without limitation, cantilever type supportstructures, torsional type support structures, and other suitablesupport structures may be used in place of the pinwheel type supportstructure discussed herein to provide a non-contact operating mode andblack state control. The formation of an exemplary light modulatordevice that provides such properties will now be discussed.

Method of Forming Non-Contact Mode Light Modulator Device

FIG. 4 illustrates a method of forming a non-contact mode lightmodulator device. The method begins by providing a substrate (step 400).The substrate serves as a base or foundation for the light modulatordevice. In particular embodiments, the substrate may be formed as partof a larger member or wafer serving as a foundation for a plurality oflight modulator devices and may be made of silicon.

Thereafter, the fixed electrode plate is formed on the substrate (step410). The electrode plate may be formed by depositing a layer ofconductive material. The layer of conductive material is then processed.This processing may include applying a bottom charge plate photoresistpattern and etching through the exposed areas. As the bottom chargeplate layer is etched, the bottom fixed electrode plate is establishedon the substrate.

A first sacrificial layer is then formed on the bottom electrode platelayer (step 420). One exemplary first sacrificial layer includes a 200angstroms layer of silicon nitrate (SiN) and a layer ofamorphous-Silicon (a-Silicon). The layer of a-Silicon may range inthickness from about 1000-7000 angstroms. According to one exemplaryembodiment, the a-Silicon layer is approximately 3300 angstroms thick.The first sacrificial layer is then processed to form flexure vias thatextend through first sacrificial layer to the substrate. These flexurevias correspond in shape to the bottom portion of the posts (235; FIGS.2A-2B).

The flexures are then formed (step 430) by depositing a layer of flexurematerial, applying a flexure photoresist pattern, and etching through tothe first sacrificial layer. The resulting flexures are thus formed ontop of the first sacrificial layer.

The reflective plate is then formed (step 440). The reflective platelayer is deposited on the flexures, thereby coupling the flexures to thereflective plate. The reflective plate layer then has a photoresistpattern applied thereto and etched to establish the reflective plate andremove material from the flexure vias.

Once the reflective plate has been formed, a second sacrificial layer(450) is formed on the reflective plate layer. Thereafter, the posts areformed (step 460). The posts are formed by first applying a post viaphotoresist pattern to the second sacrificial layer. The post viaphotoresist pattern includes exposed areas above the flexure vias. Theseexposed areas are then etched, such that post vias are formed thatextend to the bottom of the flexure vias previously formed. A layer ofpost material is then deposited in the post vias. Thereafter, a postformation photoresist pattern is applied to the layer of post material.The post photoresist pattern positively covers the post vias.Thereafter, the exposed layer of post material is etched through to theremaining second sacrificial layer, which may range in thickness fromabout 500-3000 angstroms.

The partially reflective top plate is then formed (step 470) on thesecond sacrificial layer and posts. Once this structure has been formed,the first sacrificial layer, the flexure space sacrificial layer (625),and the second sacrificial layer (635) may be removed (step 480),thereby establishing the electrostatic gap, the flexure space, and theoptical gaps discussed above.

The resulting light modulator device includes a reflective plate movablysupported by flexures. The movement of the reflective plate in responseto an electrostatic force controls the size of the electrical gap andthe optical gap. This control is accomplished while minimizing oreliminating contact between the reflective plate and other parts of thelight modulator device.

Piezo-Electric and Magnetically Actuated Flexures

In addition, other actuation mechanisms may be used in place ofelectrostatic attraction. For example, FIG. 5 illustrates a lightmodulator device (200-1) that includes piezo-electrically actuatedflexures (500). The light modulator device (200-1) generally includes areflective plate (230-1) that is separated from a fixed mirror (510) byan optical gap (225-1). When the reflective plate (230-1) is in itsneutral position, the optical gap (225-1) approximately corresponds tothe black state gap of the light modulator device (200-1). The opticalgap (225-1) is then controlled by selectively controlling thepiezo-electric flexures.

The piezo-electrically actuated flexures (500) are coupled to a powersource (not shown), which selectively provides voltage thereto. Theflexures (500) expand in response to the applied voltage, therebycausing the reflective plate (230-1) to move away from the fixed mirror(510), thereby enlarging the optical gap (225-1). As previouslydiscussed, controlling the size of the optical gap (225-1) controls thecharacteristics of light output by the light modulator device (200-1).Accordingly, these light output characteristics, including black state,may be controlled while minimizing or eliminating contact between thereflective plate (230-1) and other parts of the light modulator device(200-1).

In addition, magnetic control may also be used to provide black stateand other color outputs from a light modulator device. As shown in FIG.6, a light modulator device (200-2) is shown that includes a magneticreflective plate (205-2) and a fixed magnetic plate (600) separated by amagnetic gap (610). The magnetic reflective plate (205-2) is shown in aneutral position in which field symmetry exists between the magneticreflective plate (205-2) and the fixed magnetic plate (600). In thisposition, the magnetic reflective plate (205-2) is separated from thetop plate (220-2) by an optical gap (225-2). This configuration allowsthe light modulator device to produce a black state response whileminimizing or eliminating the contact between the magnetic reflectiveplate (205-2) and other parts of the light modulator device.

The magnetic reflective plate (205-2) is drawn toward the fixed magneticplate (500) by increasing the magnetic B field strength of magneticplate (600) thereby increasing the field gradient between the twoplates. The magnetic B field strength is varied by changing the magneticH field applied to a fixed magnetic plate by changing the current in anelectro-magnet coil (not shown) that surrounds the fixed magnetic plate.As the magnetic reflective plate (205-2) is drawn toward the fixedmagnetic plate (600), the optical gap (225-2) is varied, therebyeffecting modulation of light that enters the light modulator device(200-2). Accordingly, the light output characteristics of the lightmodulator device (200-2), including black state, may be controlled whileminimizing or eliminating contact between the magnetic reflective plate(220-2) and other parts of the light modulator device (200-2).Accordingly, several different actuation mechanisms may be used tooperate in non-contact modes to provide color responses, including blackstate responses.

In conclusion, several exemplary light modulator devices are describedherein that may improve the reliability of a display system by providingnon-contact operation. Non-contact operation refers to minimizing oreliminating contact between individual parts or components of the lightmodulator device, such as a reflective plate. Non-contact operationminimizes stiction or spot welding associated with contact betweenindividual components or parts of the light modulator device. Accordingto several exemplary embodiments, an optical gap and an electrical gapare separated to provide non-contact operation.

The sizes of the optical gap and electrical gap are varied by varyingthe position of a reflective plate. Several different support structuresmay be used to support the reflective plate as it moves through itsoperating range. Further, according to several exemplary embodiments,the neutral position of the reflective plate approximately correspondsto the black state position of the light modulator device. In some ofsuch embodiments, the position of the reflective plate is controlled byelectrostatic forces. Other embodiments make use of piezo-electricactuators or magnetically controlled actuators to control the positionof the reflective plate.

ALTERNATIVE EMBODIMENTS

Other embodiments are possible that establish a black state responsewhile maintaining non-contact operation of the components of the lightmodulator device. One of these exemplary embodiments will now bediscussed.

FIG. 7 illustrates a schematic view of display system (700) in whichfirst and second light modulator devices (710-1, 710-2) are placed inseries. In such a system, white light, which includes red, green, andblue components (720-1, 720-2, 720-3) is directed to the first lightmodulator device (710-1). In providing a black state response, the firstlight modulator device (710-1) may be operated to provide an optical gapof approximately 3800 angstroms, which corresponds to the transmissionof the blue component (720-3) and an absorption of a substantial portionof the red and green components (720-1, 720-2) of the incoming whitelight. The blue component is then directed to the second light modulatordevice (710-2) which may be operated to establish a gap of approximately3000 angstroms. In such a case, the blue component would be absorbed bythe device, such that a black state response would be detected on adisplay (730).

During periods of non-black state response, the gaps of first lightmodulator device (720-1) and the second light modulator device (710-2),are controlled to the same optical gap spacing to provide color responseto the display (730). Accordingly, the present display system (700)provides for black state responses while reducing or eliminating contactbetween components of the individual light modulator devices.

Further, to this point single posts have been described. Those of skillin the art will appreciate that separate posts may be used to supportthe top plate (220) and the reflective plate (205). In particular, FIG.8 illustrates a light modulator device (200-3) in which inner posts(240) are used to support the reflective plate (205) while outer posts(242) are used to support the top plate (220).

The preceding description has been presented only to illustrate anddescribe the present method and apparatus. It is not intended to beexhaustive or to limit the disclosure to any precise form disclosed.Many modifications and variations are possible in light of the aboveteaching. It is intended that the scope of the disclosure be defined bythe following claims.

1. A micro-electro mechanical light modulator device, comprising: amovable reflective plate; a fixed partial reflective plate; an opticalgap defined between said reflective plate and said fixed plate, and anactuator configured to move said reflective plate through an operatingrange wherein a neutral state position of said reflective plateapproximately corresponds to a black state value of said optical gap. 2.The device of claim 1, wherein said optical gap at neutral stateposition is approximately 50-200 nm.
 3. The device of claim 1, whereinsaid optical gap at said neutral state position is approximately 100 nm.4. The device of claim 1, wherein said reflective plate comprises areflective electrode plate and said actuator includes said reflectiveplate and a fixed electrode plate separated by a non-optical gap.
 5. Thedevice of claim 4, wherein a size of said non-optical gap is controlledby controlling the bias of an electric field established between saidmovable reflective plate and said fixed electrode plate.
 6. The deviceof claim 4, wherein decreasing the size of said non-optical gapincreases the size of said optical gap and increasing the size of saidnon-optical gap decreases the size of said optical gap.
 7. The device ofclaim 4, wherein said electrical gap at a neutral state position is atleast three times larger than an operating displacement range of saidreflective plate.
 8. The device of claim 4, and further comprising atleast one flexure supporting said reflective plate with respect to saidpartial reflective plate and said fixed charge plate.
 9. The device ofclaim 8, and further comprising a plurality of flexures supporting saidreflective plate and further comprising a plurality of posts supportingsaid flexures, said posts and flexures being arranged in a pinwheelconfiguration.
 10. The device of claim 8, and further comprising aplurality of flexures supporting said reflective plate and furthercomprising a plurality of posts supporting said flexures, said flexuresconfigured to act as cantilevers for supporting said reflective plate.11. The device of claim 10, wherein said flexures are configured tosuspend said reflective plate above said fixed electrode plate and tosuspend said reflective plate below said semi-reflective top plate. 12.The device of claim 8, wherein said flexure comprises at least onetorsional flexure.
 13. The device of claim 1, wherein said actuatorcomprises at least one piezo-electric actuator.
 14. The device of claim13, wherein said piezo-electric actuator comprises piezo-electricflexures.
 15. The device of claim 1, wherein said actuator comprises amagnetically actuated actuator.
 16. The device of claim 15, wherein saidmagnetically actuated actuator comprises a magnetic reflective plate anda fixed magnetic plate separated by a magnetic gap, and a top plateseparated from said magnetic reflective plate by an optical gap.
 17. Amicro-electro mechanical light modulator device, comprising: a movablereflective plate; a fixed partial reflective plate; an optical gapdefined between said reflective plate and said fixed partial reflectiveplate, and a non-optical gap defined between said movable reflectiveplate and a fixed electrode plate; and an actuator configured to movesaid reflective plate through an operating range wherein a neutral stateposition of said reflective plate is smaller than a black state value ofsaid optical gap.
 18. The device of claim 17, wherein said movablereflective plate and said fixed partial reflective plate are coupled toa same voltage source.
 19. The device of claim 17, wherein said movablereflective plate and said fixed partial reflective plate are coupled todifferent voltage sources.
 20. The device of claim 17, wherein a size ofsaid non-optical gap is controlled by selectively establishingelectrostatic charges on said movable reflective plate and said fixedelectrode plate.
 21. A micro-electro mechanical light modulator device,comprising: a fixed charge plate; a reflective plate supported by aflexure; a top semi-reflective plate; an optical gap between saidsemi-reflective plate and said reflective plate; and an electrical gapbetween said reflective plate and said fixed charge plate wherein aneutral state position of said reflective plate with respect to said topsemi-reflective plate and said fixed charge plate substantiallycorresponds to a black state position of said reflective plate.
 22. Thedevice of claim 21, and further comprising a plurality of posts coupledto said flexures to suspend said reflective plate above said fixedcharge plate.
 23. The device of claim 22, and further comprising aplurality of posts coupled to said top semi-reflective plate forsupporting said top semi-reflective plate above said reflective plate.24. The device of claim 22, and further comprising a plurality of postscoupled to said flexures to suspend said reflective plate above saidfixed charge plate, said posts further being coupled to said topsemi-reflective plate for supporting said top semi-reflective plateabove said reflective plate.
 25. The device of claim 21, wherein saidoptical gap at neutral state position is approximately 50-200 nm. 26.The device of claim 21, wherein said optical gap is about 100 nm whensaid reflective plate is in said neutral state position.
 27. The deviceof claim 22, and further comprising a plurality of flexures supportingsaid reflective plate and further comprising a plurality of postssupporting said flexures, said flexures configured to act as cantileversfor supporting said reflective plate.
 28. The device of claim 27,wherein said flexures are configured to suspend said reflective plateabove said fixed electrode plate and to suspend said reflective platebelow said semi-reflective top plate.
 29. The device of claim 26,wherein said electrical gap in said neutral position is approximatelythree times an operational displacement range of the reflective plate.30. A micro-electro mechanical light modulator device, comprising: amovable reflective plate; a fixed partial reflective plate; an opticalgap defined between said reflective plate and said partial reflectiveplate, and an actuator configured to move said reflective plate throughan operating range wherein said actuator is configured to drive saidreflective plate in a direction of increasing a size of said opticalgap; wherein a neutral stare position of said reflective plateapproximately corresponds to a black state value of said optical gap.31. The device of claim 30, wherein said actuator is an electrostaticactuator configured to move said reflective plate through an operatingrange without said reflective plate contacting said fixed partialreflective plate or said electrostatic actuator.
 32. The device of claim30, wherein said actuator is a magnetic actuator configured to move saidreflective plate through an operating range without said reflectiveplate contacting said fixed partial reflective plate or said magneticactuator.
 33. The device of claim 30, wherein said actuator is apiezo-electric actuator configured to move said reflective plate throughan operating range without said reflective plate contacting said fixedpartial reflective plate or said piezo-electric actuator.
 34. Amicro-electro mechanical light modulator device, comprising: a movablereflective plate; a fixed partial reflective plate; an optical gapdefined between said reflective plate and said fixed plate, and a springconfigured to provide a restoring force in the direction towards saidpartial reflector.
 35. The device of claim 34, and further comprising anactuator and a non-optical gap defined between said actuator and saidmovable reflective plate.
 36. The device of claim 35, wherein saidactuator is an electrostatic actuator configured to move said reflectiveplate through an operating range without said reflective platecontacting said fixed partial reflective plate or said electrostaticactuator.
 37. The device of claim 35, wherein said actuator is amagnetic actuator configured to move said reflective plate through anoperating range without said reflective plate contacting said fixedpartial reflective plate or said magnetic actuator.
 38. The device ofclaim 35, wherein said actuator is a piezo-electric actuator configuredto move said reflective plate through an operating range without saidreflective plate contacting said fixed partial reflective plate or saidpiezo-electric actuator.
 39. The device of claim 1, wherein, when in ablack state, said optical gap absorbs light across a visible spectrum.40. The device of claim 17, wherein, when in a black state, said opticalgap absorbs light across a visible spectrum.
 41. The device of claim 21,wherein, when in a black state position, said optical gap absorbs lightacross a visible spectrum.
 42. The device of claim 30, wherein, when ina black state, said optical gap absorbs light across a visible spectrum.43. The device of claim 34, wherein, when said spring is not exerting arestoring force, said optical gap is in a black state and absorbs lightacross a visible spectrum.